Aerosol provision systems such as e-cigarettes generally contain a reservoir of a source liquid containing a formulation, typically including nicotine, for which an aerosol is generated, e.g. through vaporization or other means. Thus an aerosol source for an aerosol provision system may comprise a heater coupled to a portion of the source liquid from the reservoir. When a user inhales on the device, the heater is activated to vaporize a small amount of the source liquid, which is thus converted to an aerosol for inhalation by the user. More particularly, such devices are usually provided with one or more air inlet holes located away from a mouthpiece of the system. When a user sucks on the mouthpiece, air is drawn in through the inlet holes and past the aerosol source. There is a flow path connecting between the aerosol source and an opening in the mouthpiece so that air drawn past the aerosol source continues along the flow path to the mouthpiece opening, carrying some of the aerosol from the aerosol source with it. The aerosol-carrying air exits the aerosol provision system through the mouthpiece opening for inhalation by the user.
Typically, aerosol provision systems such e-cigarettes contain an aerosol generating component, such as a heater. The liquid source is generally arranged within the system such that it can access the aerosol generating component. For example, it may be that the aerosol generating component is a wire which is heated during use of the device. As a result of the contact between the liquid formulation and the wire, when the wire is hearted during use the liquid formulation is vaporized and subsequently condenses into an aerosol which is then inhaled by the user. The means by which the liquid formulation can contact the wire may vary. It is not uncommon for the liquid source to be stored in a wadding or other type of holding matrix. This wadding or matrix then either itself directly contacts the heating wire, or alternatively it may be that a further “wick” is in contact with both the wadding and the heating wire. This wick serves to draw the liquid formulation from the wadding to the heating wire during use.
Other types of systems do not employ wadding to hold the liquid formulation. Instead, in these systems the liquid formulation is held freely in a tank or other storage area and is directly fed to the heating wire (which may itself include a wicking core to assist in holding the liquid formulation in proximity to the wire). Such “direct flow” systems may have disadvantages associated with leakage. Other systems which may be less prone to leakage include the liquid formulation held freely in a tank or other storage area, but include means to prevent the “direct flow” of the liquid formulation to the heating wire. However, it has been found that the above systems employing the “free” storage of the liquid formulation may lead to the generation of aerosols with certain degradation products.
Accordingly there remains a need for aerosol provision systems which seek to ameliorate some of the issues discussed above.